Extensible ladder construction

ABSTRACT

An extensible ladder construction of a type employing first and second sections extensible lengthwise relative to each other wherein the sections each comprise a pair of laterally spaced elongated stringers and tread members uniformly spaced longitudinally of each section and carried at their opposite ends by the stringers is arranged whereby the stringers are of channel shaped cross section to provide, in each instance, a web and parallel side flanges, the stringers of the first and second sections being turned 180* relative to each other and with the ends of tread members from both of the first and second sections disposed between the flanges of the stringers of the first section so as to retain the two sections in guided relation. Accordingly, one pair of stringers includes a guide channel for receiving a flange and the ends of the laterally extending tread members of another pair of stringers so as to provide a double width tread construction while increasing the thickness of the ladder on the order of no more than 50 percent. Means for lifting one section with respect to the other are provided which are movable with rotation of a pulley and operable therewith for engaging a portion of a latch means so as to move the latch between advanced and retracted positions for engaging and releasing the two sections. A slip drive means interposed between the pulley and the last named means permits relative movement between the last named means and the pulley during raising and lowering one section upon engagement of that section with the latch means.

United States Patent [72] Inventor Merritt A. Robinson Marin County, Calif. [21] Appl. No. 89,546 [22] Filed Nov. 16, I970 [45] Patented Dec. 14, 1971 [73} Assignee Industrial Ladder Company Oakland, Calii.

I54] EXTENSIBLE LADDER CONSTRUCTION 6 Claims, I2 Drawing Figs.

[52] U.S.Cl 182/212 [51] Int. Cl. E06c 1/12 [50] Field oi Search 182/212, 207, 209, 210, 211

[56] References Cited UNITED STATES PATENTS 1,949,972 3/1934 Murphy 182/212 2,559,992 7/1951 Painter.. 182/213 3,291,258 12/1966 Twi1ley.. 182/211 3,481,428 12/1969 Merritt 182/207 Primary Examiner Reinaldo P. Machado Attorney-Flehr, Hohbach, Test, Albritton & Herbert ABSTRACT: An extensible ladder construction of a type employing first and second sections extensible lengthwise relative to each other wherein the sections each comprise a pair of laterally spaced elongated stringers and tread members uniformly spaced longitudinally of each section and carried at their opposite ends by the stringers is arranged whereby the stringers are of channel shaped cross section to provide, in each instance, a web and parallel side flanges, the stringers of the first and second sections being turned 180relative to each other and with the ends of tread members from both of the first and second sections disposed between the flanges of the stringers of the first section so as to retain the two sections in guided relation. Accordingly, one pair of stringers includes a guide channel for receiving a. flange and the ends of the laterally extending tread members ofaanother pair of stringers so as to provide a double width tread construction while increasing the thickness of the ladder on the order of no more than 50 percent. Means for lifting one section with respect to the other are provided which are movable with rotation of a pulley and operable therewith for engaging a portion ofa latch means so as to move the latch between advanced and retracted positions for engaging and releasing the two sections. A slip drive means interposed between the pulley and the last named means permits relative movement between the A last named means and the pulley during raising and lowering one section upon engagement of that section with the latch means.

Patent9dDec. 14, 1971 3 Sheets-Sheet 1 INVENTOR.

n W. mm m w m A f m I e y Patented Dec. 14, 1971 3 Sheets-$heet 2 O! l M 4 g 3 F 7 2 2 2 11 I: I A W liill I|| 7 A I a hIll ll H W.

INVENTOR.

Merritt A. Robinson i2, I; y Attorneys Patnted' Dec. 14, 1971 3,627,076

3 Sheets-Sheet 3 EKTlENSlllBlLE LADDER CONSTIEKUCTTON BACKGROUND OF THE llNVENTlON This invention pertains to ladder constructions and more particularly to extension ladders.

In the construction of extension ladders of a type employing a plurality of sections wherein one section is extensible with respect to another, it has typically been desirable to minimize the overall thickness of the ladder construction inasmuch as two or more ladder sections will overlap and tend to form a relatively thick ladder construction. Therefore, the problem has been to provide an extension ladder of minimal thickness.

In addition to the above, there has also been a continuing need for providing an improved latch mechanism of a type which is relatively positively acting under the hoisting action of the usual rope and pulley hoist utilized to extend one ladder section with respect to another.

Further, there has been the problem of constructing an extension ladder easily handled and operated by one man using the ladder.

SUMMARY OF THE lNVENTlON AND OBJECTS In general, there has been provided an extensible ladder construction of a type employing first and second sections extensible lengthwise relative to each other, the sections each comprising a pair of laterally spaced elongated stringers and tread members uniformly spaced longitudinally of each section and carried at their opposite ends by the stringers. The stringers are of channel-shaped cross section to provide in each instance a web and parallel side flanges, the stringers of the first and second sections being in each instance turned 180 with the ends of thread members from both the first and second sections disposed between the flanges of the stringers of the first section to retain the sections in guided relation therebetween.

in short, one pair of stringers includes a guide channel for receiving a flange and the ends of the laterally extending tread members of another pair of stringers so as to provide a double width tread construction while increasing the thickness of the ladder on the order of no rhore than 50 percent In addition to the above, there is further included a lifting means for raising and lowering one of the ladder sections relative to the other and a latching means movable between retracted and advanced positions. In the latter position the latching means serves to engage and hold the raised section relative to the other in an extended position. Slip drive means have been interposed between the first and last named means for urging the latching means toward its advanced position while permitting the latching means to be pushed or struck out of the way of the raised section while the lifting means is rais ing the same section.

Accordingly, means are provided which are movable with rotation of the pulley and operable therewith for engaging a portion of the latch means so as to move the latch means between its advanced and retracted positions. The slip drive means interposed between the pulley and the last-named means and the pulley during raising and lowering of one section (referred to as the fly section) upon engagement between the fly section and the latch means.

In general, it is an object of the present invention to provide an improved extension ladder construction.

It is another object of the invention to provide an extension ladder of considerably reduced thickness in those parts thereof where two or more sections, such as the fly and base sections, overlap.

It is another object of the present invention to provide an improved extension ladder characterized by a latch means positively operated by a hoisting pulley via a slip drive mechanism for permitting the latch means to be forced out of the path of the moving section of ladder even during times when the latch is being urged into the path.

The foregoing and other objects of the invention will become more clearly apparent from the following detailed description ofa preferred embodiment.

BRIEF DESCRllPl'llON OF THE lDlRAWiNG FlG. l is a side elevation section view of overlapping sections of an extension ladder, according to the invention;

lFlG. 2 is an elevation view ofFiG. i taken along the line 2 2 thereof;

HO. 3 is an enlarged detail view in section of aligned tread portions of two ladder sections;

lFlG. is a plan view in section taken along the line l-4l of lFllG. 3;

H68. 5, s, '7 and b show four successive stages in the positioning of a portion of the fly section of an extension ladder relative to latch means when raising the fly section lFllGS. 5, 6 and 7) and lowering same (lFllG. it) to be engaged by the latch means;

H68. 9, it ti and 12 show in side elevation four successive stages in the positioning of a portion of the fly section of an extension ladder relative to latch means when lowering the fly section relative to the base section.

DETAlLED DESClRlP'ilOl l OF It PREFERRED EMBODHMENT As shown in l-lGS. l and 2, an extension ladder is represented by the portions of a base and fly section respectively lll, 117i whereby it is to be understood that fly section l2 moves up and down along the length of base section llll.

Both sections 1111, 112 are preferably molded of a suitable rigid material such as reinforced glass fiber resin suitable rigid material such as reinforced glass fiber resin whereby the ladder will be lightweight and nonconductive to electricity thereby ensuring its safe usage in and about electrical wires.

Lifting means for raising and lowering fly section l2 relative to base section ill have been provided in the form of a hoist consisting ofa pulley. l3 and hoisting rope, chain, or cable, all referred to herein simply as a rope lid trained about pulley l3 -to form hauling and lifting reaches l6, l7 thereof. Thus, the

end oflifting reach i7 is secured to fly section H2 at the lower end thereof and the hauling reach llti is free for hauling thereon so as to hoist fly section 112 upwardly guided along base section it in telescopic fashion.

Each section llll, 112 comprises a pair of laterally spaced elongated stringers iii, l9 and tread members iii, 22 uniformly spaced longitudinally of each section llll, l2. Tread members 211, 22 are carried at their opposite ends by stringers lb, 119 and are preferably formed, for strength, in the form of a U-shaped channel configuration. The stringers lb, llil are of channel-shaped cross section to provide in each instance a web bounded by parallel side flanges 23 (for stringer l8) and M (for stringer l9).

Stringers H8, 119 are in each instance turned with one stringer flange 24' (lFlG. 4 of fly section i2 and ends 211a, 22a of tread members Zll, 22 from both the first and second sections ill. 12 disposed between flanges 23 of the stringers iii of base section it so as to retain the two sections ill, 12 in guided relation therebetween.

The ends 21a, 22a of each tread member Zll, 22 are retained in molded U-shaped sockets 26, 2'7 forming portions of the stringers MB, 119 whereby a guide channel 2% (FIGS. 3, 4) will be defined between the side surfaces of sockets 2s and the interior surface of one flanges 23.

As thus arranged, sockets 27 of stringer 19 (carrying the ends oftread members 22 therein) fit, along with flange 24', in guide channel 2% for movement along the length of base section llll.

From the foregoing, it will be readily evident that the tread portion has been doubled without increasing the thickness of the ladder substantially more than 50 percent.

As now to be described, latching means have been provided to be carried by the upper end of base section llll so as to be movable between retracted and advanced positions, and while in its advanced position serves to engage and hold fly section l2 relative to base section llll in an extended position. Slip clutch means have also been provided between pulley i3 and the latch means for urging the latch means toward its advanced position to cause it to engage the lower edge of tread members 22 while, at the same time, permitting the latching means to be pushed or struck out of the path of fly section 12 while pulley 13 is being used to raise fly section 12. The latch means is also urged by pulley 13 toward its retracted position when lowering section 12.

More particularly, as best shown in FIGS. 1 and 2, pulley 13 is mounted upon a pulley bolt 29 and retained by a hex nut 31.

An annular dog element 32 formed with a radially project ing dog portion 32a is mounted for rotation upon pulley bolt 29. A resilient disc washer or compression spring 33 is carried about pulley bolt 29 and compressed by hex nut 31 against the side surface of dog element 32. Accordingly, dog element 32 is pinched between the side face of pulley 13 and disc washer 33 so that upon rotation of pulley 13, there is a tendency to rotate dog element 32 by friction engagement between the two surfaces noted above. The friction can be enhanced by forming the confronting side face of pulley 13 and dog element 32 with irregular surface portions. However, upon engaging or restraining rotation of dog element 32, it will be readily evident that pulley 13 can continue to rotate independently thereoffor purposes described below.

Latching means have been provided and carried by base section 11 for movement between advanced and retracted positions respectively into and out of the path of fly section 12 for engaging and holding same. The latching means is operated by dog element 32 movable with the rotation of pulley 13 upon engagement between a dog portion 340 of the latch means and dog portion 320 so as to move the latch means between advanced and retracted positions.

MOre specifically, a catch member 34 formed with a detent 36 or notch (FIG. is pivotally supported to rotate with a shaft 38 carried between stringers 18 whereby catch member 34 on each end of shaft 38 can serve to pivot about the axis thereof. A pin 35 attaches catch member 34 to shaft 38 for rotation therewith. A stop pin 37, carried by each of members 34, rides in a notch 39 (FIG. 1) so as to be limited in its travel and define the advanced and retracted positions thereof. Accordingly, as shown in FIG. 1, stop pin 37 has engaged one end of notch 39 so as to dispose detent 36 directly into the path of the lower edge of tread member 22.

The lower end of catch member 34 includes a dog portion 34a disposed in the path ofdog portion 32a.

Operation of the ladder construction as described above can best be understood with reference to FIGS. 5 through 12 as now to be described.

Assuming initially a downward pull on the hauling reach 16 of rope 14 there will be counterclockwise rotation of pulley 13 and, due to the compression of the resilient annular compression spring 33, there will tend to be counterclockwise rotation of dog element 32. Ultimately, portion 320 of dog element 32 strikes dog portion 34a so as to rock catch member 34 clockwise thereby disposing detent 36 into the path of the upwardly moving fly section 12 being hoisted upwardly by reach 17. Ultimately, the upper edge of tread member 22 strikes the inclined surface 41 of catch member 34 to rotate catch member 34 in a counterclockwise direction against the frictional resistance of dog element 32 pinched between spring 33 and the side face of pulley 13 (FIG. 6).

Thus, as shown best in FIG. 6, it is readily evident that the stop pin 37 has been carried to the left side of notch 39 to permit tread member 22 to pass upwardly. However, after tread member 22 has passed beyond catch member 34, the continued downward pulling on reach 16 of rope 14 serves to reinsert detent 36 into the path of fly section 12.

However, as shown best in FIG. 8, when fly section 12 is next lowered by releasing reach 16, it will be readily evident that the lower edge of tread member 22 will engage detent 36 as dog element 32 continues to rotate clockwise away from dog portion 34a. (As will be seen further below. if dog element 32 rotates for a full revolution (FlG.ll), catch 34 will be retracted.)

As shown in FIG. 8, there will be present a certain amount of slack in reach 17 so that it would be dangerous to release catches 34 without first tightening reach 17.

Accordingly, as shown in FIG. 9, downward hauling on reach 16 again rotates dog element 32 into engagement with dog portion 340 before releasing catch member 34. Sub

sequently, catch member 34 is rotated clockwise about shaft 38 as reach 17 hoists fly section 12 upwardly out of detents 36.

Clockwise rotation of catch member 34 is limited, of course, by stop pin 37 as it engages the right hand edge of notch 39. Upon being arrested by this interengagement of stop pin 37 with notch 39, pulley 13 can continue to be rotated by further downward hauling on reach 16 by virtue of the interposition of the slip drive fonned by means of the spring washer 33 and frictional engagement of dog element 32 between pulley 13 and washer 33.

As thus arranged, catch member 34 will be in an appropriate position to receive the downward moving edge of tread member 22 unless it is desired to release catch member 34. Such release is accomplished as shown in FIG. 10 by extending tread member 22 a substantial distance beyond catch member 34 whereby upward movement of reach 16 (FIG. 1 1) serves to rotate dog portion 32a substantially a full revolution from its position as shown in FIG. 10 and into engagement with the reverse side of dog portion 34a thereby retracting catch members 34 in a counterclockwise direction (FIG. 11). In this manner, catch members 34 have been retracted out of the way of the downwardly moving tread member 22 so that, as shown in FIG. 12, tread member 22 passes clear of catch members 34 and fly section 12 can be lowered as desired.

From the foregoing, it will be readily evident that there has been provided an improved extension ladder wherein release of the catch members is accomplished merely by the two steps of advancing the fly section a substantial distance up the base section on the order of the spacing between successive tread members or rungs of the fly section followed by downward release of the fly section whereby dog portions 32a will engage the dog portions 34a and retract catch members 34.

In order to relock sections 11, 12, fly section 12 is simply raised the distance on the order of at least one-half rung of the ladder whereby dog element 32 will have been returned to the FIG. 5 position.

Further, it will be evident that the rope-actuated locking device allows full control of the ladder directly from the rope during all of the functional operations of raising, lowering, locking and unlocking the two ladder sections. In addition, the fly section 12 must travel a substantial distance. of the order of one-third to one-half the space between rungs before the locking mechanism can act to retract catch members 34. Thus, this provides a feature which allows the ladder to descend without the lock elements striking each of the rungs on the one hand while permitting the ladder to be locked by simply actuating the rope 14 on the other.

In addition, it will be readily evident that the extension ladder is of a considerably reduced thickness as compared to conventional extension ladders. Accordingly, a double width tread is provided by aligning the tread members 21, 22 in a common plane while the overall thickness of the ladder is increased on the order of not more than 50 percent.

Iclaim:

1. In an extensible ladder, first and second ladder sections extensible lengthwise relative to each other to form a ladder of selectively adjustable length, each of said sections comprising a pair of laterally spaced elongated stringers and thread members uniformly spaced longitudinally of each section and carried at their opposite ends by said stringers, said stringers being of channel-shaped cross section to provide in each instance a web and parallel side flanges, the channel-shaped cross sections of the stringers of said first and second sections being opposed to one another with one of the flanges and an end of the tread members of said second section being disposed within each of the channels of said first section, the ends of the tread members of said first section also being disposed within each of the channels of said first section, one side of the ends of the last-named tread members and a flange of each of the channels of said first section defining a guideway to receive a flange and the ends of the tread members of said second section to provide a double width tread while increasing the ladder thickness and amount not substantially greater than 50 percent of said first section.

2. In an extensible ladder first and second ladder sections extensible lengthwise relative to each other, each of said sections comprising a pair of laterally spaced elongated stringers and tread members uniformly spaced longitudinally of each section and carried at their opposite ends by said stringers, said stringers of said first section being of channel-shaped cross section to provide a web and parallel side flanges, the stringers of said first and second sections being turned 180 with the ends of tread members from both said first and second sections disposed between the flanges of the stringers of said first section to retain said sections in guided relation therebetween.

3. In an extensible ladder, first and second ladder sections extensible lengthwise relative to each other, said first section comprising a pair of elongated stringer members of channelshaped cross section to provide a web and parallel side flanges, tread members uniformly spaced longitudinally of said first section and carried at their opposite ends by said stringers, the ends of said tread members on each side of said first section being spaced from a common one of said side flanges on said side to form a guide channel along said stringers on each side of said first section and defined on each side between the common one of said side flanges and ends of said tread members, a second ladder section comprising a pair of elongated stringer members each including a side flange, a web portion and tread members uniformly spaced longitudinally of said second section and carried at their opposite ends by the last-named said web portions, the last-named said flanges and the ends of the last-named tread members being disposed in guided relation in said guide channels,

4. In an extensible ladder construction according to claim 3 latching means carried by one of said sections and serving to engage the other of said sections at positions disposing the tread members of both sections at a common level so as to provide a double width tread for each adjacent pair of said tread members.

5. In an extensible ladder according to claim 3 further including lifting means for raising and lowering one of said sections relative to the other, and latching means movable between retracted and advanced positions and in the latter position serving to engage and hold said one section relative to the other in an extended position, and slip drive means interposed between the first and last-named said means for urging said latching means toward said advanced position while permitting said latching means to be urged out of the path of said one section while said lifting means raises said one section.

6. In an extensible ladder of a type having first and second ladder sections extensible lengthwise relative to each other, and having a rope and pulley hoist for raising and lowering one of said sections relative to the other, said pulley being carried by said other of said sections at the upper end thereof and said rope being trained about said pulley, one end of said rope being secured to said one section and the other end being free for hauling, the improvement comprising latch means carried by said other section and movable between advanced and retracted positions respectively into and out of the path of said one section for engaging and holding same relative to said other section, means movable with rotation of said pulley and operable therewith for engaging a portion of said latch means to move same between said advanced and retracted positions, and slip drive means interposed between said pulley and the last-named said means to permit relative movement between the last-named said means and said pulley during raising and lowering of said one section upon engagement between said one section and said latch means. 

1. In an extensible ladder, first and second ladder sections extensible lengthwise relative to each other to form a ladder of selectively adjustable length, each of said sections comprising a pair of laterally spaced elongated stringers and tread members uniformly spaced longitudinally of each section and carried at their opposite ends by said stringers, said stringers being of channel-shaped cross section to provide in each instance a web and parallel side flanges, the channel-shaped cross sections of the stringers of said first and second sections being opposed to one another with one of the flanges and an end of the tread members of said second section being disposed within each of the channels of said first section, the ends of the tread members of said first section also being disposed within each of the channels of said first section, one side of the ends of the last named tread members and a flange of each of the channels of said first section defining a guideway to receive a flange and the ends of the tread members of said second section to provide a double width tread while increasing the ladder thickness an amount not substantially greater than 50 percent of said first section.
 2. In an extensible ladder first and second ladder sections extensible lengthwise relative to each other, each of said sections comprising a pair of laterally spaced elongated stringers and tread members uniformly spaced longitudinally of each section and carried at their opposite ends by said stringers, said stringers of said first section being of channel shaped cross section to provide a web and parallel side flanges, the stringers of said first and second sections being turned 180* with the ends of tread members from both said first and second sections disposed between the flanges of the stringers of said first section to retain said sections in guided relation therebetween.
 3. In an extensible ladder, first and second ladder sections extensible lengthwise relative to each other, said first section comprising a pair of elongated stringer members of channel shaped cross section to provide a web and parallel side flanges, tread members uniformly spaced longitudinally of said first section and cArried at their opposite ends by said stringers, the ends of said tread members on each side of said first section being spaced from a common one of said side flanges on said side to form a guide channel along said stringers on each side of said first section and defined on each side between the common one of said side flanges and ends of said tread members, a second ladder section comprising a pair of elongated stringer members each including a side flange, a web portion and tread members uniformly spaced longitudinally of said second section and carried at their opposite ends by the last-named said web portions, the last-named said flanges and the ends of the last-named tread members being disposed in guided relation in said guide channels.
 4. In an extensible ladder construction according to claim 3 latching means carried by one of said sections and serving to engage the other of said sections at positions disposing the tread members of both sections at a common level so as to provide a double width tread for each adjacent pair of said tread members.
 5. In an extensible ladder according to claim 3 further including lifting means for raising and lowering one of said sections relative to the other, and latching means movable between retracted and advanced positions and in the latter position serving to engage and hold said one section relative to the other in an extended position, and slip drive means interposed between the first and last-named said means for urging said latching means toward said advanced position while permitting said latching means to be urged out of the path of said one section while said lifting means raises said one section.
 6. In an extensible ladder of a type having first and second ladder sections extensible lengthwise relative to each other, and having a rope and pulley hoist for raising and lowering one of said sections relative to the other, said pulley being carried by said other of said sections at the upper end thereof and said rope being trained about said pulley, one end of said rope being secured to said one section and the other end being free for hauling, the improvement comprising latch means carried by said other section and movable between advanced and retracted positions respectively into and out of the path of said one section for engaging and holding same relative to said other section, means movable with rotation of said pulley and operable therewith for engaging a portion of said latch means to move same between said advanced and retracted positions, and slip drive means interposed between said pulley and the last-named said means to permit relative movement between the last-named said means and said pulley during raising and lowering of said one section upon engagement between said one section and said latch means. 